Circuit interrupter



May 25, 948 w. M. LEEDS ETAL 2,442,910

C IRCUIT I NTERRUPTER Filed Dec. 24, 1943 3 Sheets-Sheet 1 WITNESSES: 47INVENTOR5 M nfhrap M Zeeas and g fier 'am/n p Bare/'1 May 25, 1948. w,M, LE D HAL 2,442,010

CIRCUIT INTERRUPTER Filed Dec. 24, 1945 3 Sheets-Sheet 3 g 6/ g g 6/ T 3XI N 58 5 iii 1 WITNESSES: INVENTORS c Mhihrap/W. Leeds and I Ben am/nPEG/(6f:

Patented May 25, 1948 UNITED STATES PATENT OF FlCE CIRCUITlNTEliRflFT-Eli Winthrop M. Leeds, Wilkinsliurg', and- Benjamin" P.Baker, Turtle Creek, Paaassignors t'o Westinghouse Electric Corporation;East Pittsburgh; Pa., a corporation of Pennsylvania Application December24, 1943, Serial' No. 515,536

Claims; 1

Thisinvention relates to circuit interrupters, and, more particularly,to circuit interrupters-of the type having arc extinguishing structuresin Whichfluid is forced into the are stream to effect rapid extinctionof the are.

It wasfound in testing a circuit interrupter of the type having anozzle-shaped stationary contact, from which a movable contact waswithdrawn and having aplurality of laterally disposed inlet passagesspaced along the path ofmovement of the movable contact, somewhatsimilar tothat shown in U. S. Patent 2,304,529 issued December 8, 1942,to Benjamin P. Baker, andassigned to the same assignee of thisinvention, that the greater proportion of the oil would flow through theinlet passage adjacent the vented-'nozzle-shaped contact. It was feltthat this greater proportion of flow, which took place adjacent thestationary contact, could be attributed to the restriction of the lowerinlet passages by the moving contact and the-back pressure fromgasproduced by the arc. The disadvantage which resulted wasinadequatescavenging of the whole arc length by oil flow; It is desirable to havethe arc extinguishing fluid traverse the entire arc space whatever theposition of the moving contact. Furthermore, during a flushingoperationtaken on no-load' operation of the interrupter, itis alsodesirableto have the flushing. oil pass throughthe entire arcing region.

It isageneral object of our invention to provide a solution for thisproblem.

Another object is to provide an improved circuit interrupter of'the typehaving a plurality of passages disposed along the path of move-- ment ofthe moving contact, and to provide valve means for controlling the flowof fluid through the plurality of passages. Preferably, it is desirableto provide valve means which are movable in responseto motion of themovable contact which successively opens the passages to permit the flowof fluid therethrough.

Another object is to provide an improved circuit interrupter of the typewhich causes a flow of fluid substantially transversely of the are at alevel with a moving point in the arc. The moving point may move at aspeed which is proportional to the speed of movement of the movablecontact.

Another object is to provide an improved cir cuit interrupter of thetype having separablecontact means to establish an are. We associate achamber with the circuit interrupter havinga volume which iscontract'able duringthe opening movement-of the movable contact means,and

2. which is expandable during the closingmovement thereof. We associatevalve means with the chamber for causingunidirectional circulation offiuid through the chamberduring a'complete operation of the interrupter.

Furtherfobiectswill become apparent upon a reading of the followingspecification taken in conjunction with the drawings, in which:

Figure 1' is acircuitinterrupter embodying our invention and shownintheclosedcircuit position;

Fig. 2" is an enlarged .vertical sectional view through" one of the arcextinguishing units of Fig. 1, the contactsbeing shownin the partly opencircuit position;

Fig. his; a View in sectiontaken-on the line 1II ;-;-III of Fi 2-;

Fig fl is a view in section taken on the line IV IV of Fig. 2'; a

Fig. 5 is a circuit interrupter embodying a modification of" ourinvention taken on the line V- V' of Fig. 6,-the"contacts beingshown inthe partly open' circuit position;

Fig; 6 is a -view in section taken on the line VI -VI of' Fig.- 5;

Fig; 7 is'anotherinodification of our invention takenon"the-line--VIIVII'of Fig. 8, the contacts being shown in thepartlyopen circuit position;

8-isa-view in-section taken on the line Fig. 9 is a view in sectiontaken on'the line IX'IX- of Fig. 7;

Fig. -10-1s stillanotherembodiment of our invention; thecontacts againbeing shown in the partly open circuit position Fig. 11 isa view insection'taken on the line XI XI of-Fig. 10; and

Fig. 12 is 'a view in section taken on the line XII-XI} of Fig. 10'.

Referrin'g' to the drawings and, more particularly, to Fig-l 1, thereference'numeral I designates a tank filled to' the'level 2'with asuitable arc extinguishing: fluid, in this instance oil. Depending fromthe cover'3'of the tank I area pair of terminal bushings 4 which enclosea pair of terminal studs, not shown. Threaded to the lower end'oftheterminal studs are a pair of apertured contact feet 5 which areclamped to the terminal studs by clamping studs 6. The contact feet 5support a pair of arc extinguishing units, generally designated by thereference numeral 1; which arebridged in the'closed circuit position; asshown'inFigi' 1, by a conducting briclgin'g'bar'B; which is reciprocallyoperated in a vertical direction a by an insulating operating rod 9 toeffect the opening and closing of the circuit through the interrupter.The full open-circuit position of the interrupter is shown by the dottedlines II) of Fig. 1. At the opposed outer ends of the bridging bar 8 arethe movable contacts II of the interrupter. Since the two units 1 areidentical, a description of only one will sutfice.

Bolts I3, which extend through the contact feet 5, secure a hollowstationary contact support I4 in place (see Fig. 2). Threadedly securedto the contact support I4 is an annular removable arc resistingstationary contact I5 having an aperture I6 therethrough for forming avent. As shown in Fig. 2, insulating tie rods I1 and nuts I8 secure agrid structure, generally designated by the reference numeral I9, to thestationary contact support I4.

In this instance the grid structure I9 comprises two types of plates.The first type is herein called an insulating orifice plate and isdesignated by the reference numeral 20 in Fig. 2. The orifice plate 20has an aperture 2I centrally formed therein through which moves themovable contact I I. The second type of plate comprises a plurality, inthis instance four, segmental insulating plates 23 more clearly shown bythe dotted lines in Fig. 4. The segmental insulating plates 23 arerigidly secured in place by the tie rods II and they form a plurality ofinlet passages 24 between each pair of orifice plates 20.

The movable contact II separates from the stationary contact I5 toestablish an are 25 as more clearly shown in Fig. 2. We provide movablevalve means comprising a cylindrical slide valve or apertured member 26,the upper end of which is guided by a portion 21 integrally formed withthe contact support I4. The lower end of the cylindrical slide valve 26is threadedly secured at 28 to an ofistanding wall 29 integrally formedwith the movable contact II. It will be observed that the cylindricalslide valve 26 and the wall 29 form a chamber, generally designated bythe reference numeral 36 in Fig. 2. The movable contact I I has apassage 32 formed therein which connects the arcing region, generallydesignated by the reference numeral 33, with the chamber 36. -It will beobserved that the are 25 has a fixed arc terminal at the stationarycontact I5 and a movable arc terminal at the tip 31 or the movablecontact II.

The cylindrical slide valve 26 and the offstanding wall 29 together forma piston member, generally designated by the reference numeral M, whichmoves in response to motion of the movable contact II within a pistonchamber, generally designated by the reference numeral 42. The pistonchamber 42 comprises an insulating cylinder 43, the upper end of whichis threadedly secured at 44 to an offstanding flange 45 integrallyformed with the stationary contact support I4. The lower end of theinsulating cylinder 43 is threadedly secured to a bottom metallic plate46 which also serves to guide the motion of the moving contact II.

In this instance four apertures 41 are provided in the cylindrical slidevalve 26 to successively cause the opening of the inlet passages 24. Itwill be observed that the apertures 41 are positioned adjacent the tip31 of the movable contact II. Consequently, as the contact I I movesdownwardly one set of inlet passages 24 is sealed up and the next set ofinlet passages 24 are opened up. Thus this arrangement permits a veryeffective use of the oil flow which must traverse the;

' against the offstanding wall 29.

entire arc space 33 whatever the position of the moving contact II.Furthermore, since oil flow is above the contact tip 31, being projectedtoward the point P, the clearance between the moving contact II and thegrid plates may be reduced to a minimum. This means more restriction ofthe are 25 for a given size contact I5, and, therefore, more effectiveare interruption.

The operation of the embodiment of our invention shown in Figs. 1-4 willnow be explained. In the closed circuit position of the interrupter asshown in Fig. l, the electrical circuit therethrough comprises left-handterminal stud, not shown, left-hand contact foot 5, stationary contactsupport I4, stationary contact I5, movable contact II, conductingbridging bar 3 through the right-hand arc extinguishing unit I in anidentical manner to the right-hand terminal stud not shown.

When it is desired to open the electrical circuit passing through theinterrupter, or in response to overload conditions existing in theelectrical circuit controlled by the interrupter, suitable operatingmechanism, not shown, is actuated to cause downward movement of theinsulating operating rod 9. The downward movement of the insulatingoperating rod 9 causes downward movement of both the movable contact IIand downward movement of the piston member El within the piston chamber42. The movement of the piston member 4I Within the piston chamber 42forces oil to flow in the direction indicated by the arrows in Figs. 2and 4. Also pressure formed by the arc 25 within the arcing region 33will act through the passage 32 provided in the movable contact I I tocommunicate with the chamber 3i] and hence act against the wall 29 tospeed up the downward movement of the movable contact II during highcurrent interruption.

In other words, we provide a diiierential piston action caused by thearcing pressure acting through the passage 32. The arcing pressure actsthrough the inlet passages 24 and upwardly However, the arcing pressurealso acts through the passage 32 and on top of the wall 29 and also ontop of the contact II. The diilerential pressure which causes a netdownward force to assist the opening operation of the movable contact IIis the arcing pressure acting across an area equal to thecross-sectional area of the lower portion of the movable contact I I.During high current interruption this additional driving force speeds upthe opening movement.

The downward movement of the piston member 4| within the piston chamber42 causes oil to flow through the four apertures 41 provided in thecylindrical slide valve 26 and through the inlet passages 24 toward apoint P, which in this instance moves at a speed equal to the speed orthe movable contact II. The oil which enters the arcing region 33 at thelevel P must then traverse the entire arcing region 33 before it ispermitted to vent through the aperture I6 provided in the stationarycontact I5 as indicated by the arrows in Fig. 2.

It will, therefore, be apparent that we have provided an interrupter inwhich there are disposed a plurality of passages 24 which terminate attheir inner end adjacent the are 25 and we provide movable valve means26 movable in response to motion of the movable contact II forcontrolling the flow of fluid through the passages 24. 'As the movablecontact II moves downward amaoro.

during. the opening operation, the. are 25. is lengthened and theapertures 41 provided in the cylindrical. Slide valve. ZILsuccessivelyopen. the passages 24.-to permit the flow of oil therethrough.

It. will be noted that. the arrangement operatestopermit oil to flowthrough the particular passagesl twhichat a particular timeterminateadjacent the ti 3.! of themovable contact II. Theflow. of oil isvsubstantially transversely of thefarc 2'5 and is directed therein at a.level with the moving point P. inthearcing region 33, which point Pmovesat a. speed which in this instance is directly equal to the speed of.movement of the movablecontact II By making the speed of movement. ofvthe movable. contact II different from the speed of movement of themovable cylindricalslide valve 25 by suitable means such as intermeshinggears, the speedof the point P could be different from the speed of. themovable contact II, For purposes of simplicity we felt it desirable tomechanically connect the slide valve 26 and the movable contact II sothat the speed of. movement of the point P would be the same as thespeed of movement of the movable contact II.

During the closing operationof the interrupter shown in Fig. 2, oil willbe drawn upwardly through valve 35. and into chamber the latter thenbeing expandedin volume. During the sub sequent opening stroke onno-loadoperation the volume of thechamber 42 diminishes and the fresh oil nowdisposed therein will move upwardly throughv the inlet passages 24 toflush carbonized products of decomposition disposed within the arcingregion 33 upwardly and out through the aperture I6 provided in thestationary contact i5. Thus during no-load operation of the interrupterthere is a complete flushing of the arcing region 33 because of thisunidire tional fiow of fresh oil through chamber 42.

In the embodiment of ourinvention shown in Figs, 5 and 6 we provide aresiliently-mounted relatively. stationary contact 52 which cooperateswith the movable contact I I to establish and lengthen an are 25. Aring-shaped plate 53, threaded to the. upper end of the cylindricalslide valve 26, forms a piston member which operates in apiston chamber42. In this embodiment ofour invention the passage formed between thesegmental insulating plates 23 form discharge .passages 54, which permitthe discharge of oil from the arcing region 33. An offstanding portion55 is integrally formed with contact H having. apertures 56 formedtherein and is threadedly secured to the lower end of cylindrical slidevalve 25. Apertures 51 are also formed in the top insulating platemember 580i the grid structure I9. The top insulating plate member 58 isthreadedly secured at 59 to a guide 60 which guides the movement of therelativelyv stationary contact 52. Apertures BI are formed in thestationary contact support 62, The stationary contact support 62 may besecured to the contact feet 5 (see Fig.1) by bolts I3 which may bethreadedly inserted into the contact support 62.

It will be apparent that the arc 25 has a fixed arc terminal atthestationary contact 52 and a movable arc terminal at the tip 31 of themovable contact II. During the. opening operation the. movable contactIl moves downwardly together with the cylindrical slide valve 25 andpiston .member 53, The downward movement of piston. member 53 withinpiston chamber 42 causes a flowof oil out of piston-chamber 42 stancemoves at the samespeed as themove 10. ment of the movable arc terminal;The direction of flow is indicated by the-arrows in Figs. Sand 6.

It. will be observed that in Figs. 2, 5'andl0 .that the vertical lengthsof the apertures 41. is sub-.

: stantiallyequalto twice the widthofthe plates 2Q, 23; Consequently, atnotime is theentrance or discharge of oil from the. arcing region 33.-

entirely prohibited, there always being atleast oneiull width of.discharge or. entrancepassage 5s, 24 through which the oil may-pass.

It will be apparent. from theabove descriptionv that in the embodimentof our-invention shown in Figs. 5 and 6, wehave providedvalve-means- 25responsive tomotionof the movable contact: I I for directing-a flow'ofoil adjacent the. fixed are terminal, through the arcingregion 33 anddis.-

charging out of the. arcing region 331adjacent the movable arc terminalat a level P which moves inthis instance at a speed directly equal-tothe 1 speedof the movablelcontact I I. As mentionedin. connection withFig. 2 intermeshing gears oriother means could be-provided'tohave thespeed-oi movementof the point PinFig. 5 different from the speedof-movement of the movable arc. terminal.

Again the valve causes a unidirectional-flow of oil through the pistonchamber 42 during a complete. operation of -.-the interrupter.

In the embodiment of our inventionshown in Figs. 7 through 9, we provideacircuitinterrupter oi modified construction having a. piston. chamsb-er generally. designatedby thereferencenw.

meral "H. Thepiston chamber II has. an enlarged portion Hand a-smaller-closedportion .753. An insulating cup-shaped member I41 is threadedlysecuredlat '55 to the .oifstanding sup port portion 55 of the movablecontact III The ofistanding support portion 55 again has aperturesv 56.formed therein.

5 ...enlarged portion I2 is threadedly secured to'an apertured supportplate It which may be secured to the contact feet f Fig. l' by anysuitable means suchas the bolts l3 shown in Fig: 1. Again the valve 35causes unidirectional. flow of oil through the piston chamber II duringeach @complete operation of the interrupter.

In Fig. '7 the grid structure I9 is movable-with the movable contact I lbeingsecured to the cupshaped member M bythe insulating tie rods I1.During the opening operation themovable contact ll, cup-shaped member 'ILand-grid-structure 59 move downwardly as a unit from the/enlargedportion I2 into thesmallerclosed portion 'IEIofthe piston chamber 1|.Thiscauses anupward flow of oil radially inwardly toward the movable arcterminal, upwardly within the arcing region 33 and outwardly through thedischarge passages 54 at a level P which, in thisinstance, is adjacentthe stationary arc terminal. It-will be apparent that the gridstructureI9 coacts with theashoulder I! to permit-the discharge of oil throughthe discharge passages 54 only ata level adjacent the fixed arc terminalIt will benoted thatthe discharge passages 54 are uncoveredsuccessively'as theylare brought below the-stationary The. upper end ofthe 7. contact tip, while the outer openings of these discharge passages54 are successively sealed off as they move below the shoulder 11integrally formed with the piston chamber 1 I.

It is also to be observed that the pressure in the exhaust chamber,generally designated by the reference numeral 18, in Fig. 7, tends toaccelerate the moving contact II by acting downwardly on the moving grid[9. The size of the apertures 1 6a determines the magnitude of thepressure in the exhaust chamber.

In the embodiment of our invention shown in Figs. 10-12, we disclose anarrangement similar to that shown in Fig. 5. However, we provide apassage 32 through the movable contact H to permit differential pistonaction to accelerate the opening movement of the movable contact llduring high current interruption. In other words, the arcing pressureacts upwardly on the ringshaped piston 53, but also acts downwardly onthe support portion 55 by actin through the passage 32. The differentialpiston area is, therefore, the area of the support portion 55 minus thearea of the ring-shaped piston member 53, and the arcing pressure actingon this differential piston area tends to accelerate the movement of themoving contact H during high current interruption.

As in Fig. 2, we have a chamber 30 which is expandable during theopening operation and contractable during closing operation. The slidevalve action of cylindrical slide valve 26 is the same as in Fig. 5.Therefore, a further description concerning this feature is notnecessary for a full understanding of this embodiment of our invention.It will be noted that in Fig. 10 the discharge of oil takes placethrough the discharge passages 54 at a level P, which level moves at thesame speed as the movable contact ll. As previously mentioned, adifferent speed ratio could be obtained by means permitting relativemovement of the contact I l with cylindrical slide valve 26, such asintermeshing gears or other suitable means well known in the art.

Although we have illustrated our invention as adapted to particularlydesirable forms of circuit interrupters which use a suitable areextinguishing liquid such as oil, it is to be clearly understood thatsome aspects of our invention are not limited to these particular typesof interrupters but are adapted to the use of any fluid which need notbe oil but could be a gas or even air. Also separate sources of pressureto drive such fluids as gases or liquids could be used instead ofrelying on piston action of the moving parts.

Although we have shown and described specific structures, it is to beclearly understood that the same were merely for purposes ofillustration and that changes and modifications may be readily made bythose skilled in the art Without departing from the spirit and scope ofthe appended claims.

We claim as our invention:

1. In a circuit interrupter, means for establishing an arc, meansdefining a plurality of stationary passages terminating at one endclosely adjacent to the arc, and a cylindrical slide valve substantiallysurrounding the are for controlling the flow of fluid through theplurality of passages.

2. In a circuit interrupter, movable means for establishing andlengthening an arc, means delining a plurality of stationary passagesterminating at one end closely adjacent to the arc, and a cylindricalslide valve substantially surrounding the are responsive to motion ofthe first- 8. mentioned means for controlling the flow of fluid throughthe plurality of passages.

3. In a circuit interrupter, an annular stationary contact, a movablecontact cooperable with the stationary contact to establish an arc,stationary means partly of insulating material for forming a pluralityof inlet passages tenninating adjacent the path of movement of themovable contact, a piston chamber containing fluid, a piston membersecured to and movable with the movable contact within the pistonchamber, the piston member having an aperture formed therein tosuccessively open the inlet passages while meanwhile closing others andthus permit fluid forced under pressure from opening movement of thepiston member to successively pass through the inlet passages to thearc, and at least part of the fluid discharging through the annularstationary contact.

4. In a circuit interrupter, a stationary con tact, a movable contactcooperable with the stationary contact to establish an arc, stationarymeans partly of insulating material forming a plurality of dischargepassages leading away from the path of movement of the movable contact,a piston member secured to and movable with the movable contact, thepiston member having an aperture formed therein to successively open thedischarge passages during the opening operation while meanwhileclosingothers, the piston member forcing the fluid adjacent the stationarycontact toward the arc and at least part of the fluid discharging awayfrom the are through the discharge passages upon the opening thereof.

5. In a circuit interrupter, a stationary contact, a movable tubularcontact cooperable with the stationary contact to establish an arc,stationary means partly of insulating material forming a plurality ofdischarge passages leading away from the path of movement of the movabletubular contact, a difierential piston member secured to and movablewith the movable contact, the differential piston member having anaperture formed therein to successively open the discharge passagesduring the opening operation while meanwhile closing others, thedifferential piston member being driven by arcing pressure actingthrough the movable tubular contact to force fluid adjacent thestationary contact toward the arc, and at least part of the fluiddischarging away from the arc through the discharge passages upon theopening thereof.

6. In a circuit interrupter, a piston chamber having an enlarged portionand a smaller closed portion, a stationary contact and a movable contactboth disposed within the piston chamber and cooper-able to establish anare, a grid structure partly of insulating material and secured to andmovable with the movable contact from the enlarged portion of the pistonchamber to the smaller closed portion thereof, the grid structureoperating as a piston within the piston chamber to force fluid adjacentthe movable contact and into the arc, the grid structure forming aplurality of discharge passages for the discharge of fluid from saidarc, the discharge passages being successively closed upon openingmovement of the grid structure into the smaller portion of the pistonchamber.

7. In a circuit interrupter, means at least partially of insulatingmaterial forming an arc passage, means for establishing an arc withinthe arc passage, the'first-mentioned means also providing a plurality offluid passages disposed axially along the arc passage whereby fluid mayflow 9 through the fluid passages, and means for successivelyopeningth'e fluid passages one by one While at the same timesuccessively closing others of said fluid passages so that fluid maypass only through the fluid passages which are opened by saidlast-mentioned means.

8. In a circuit interrupter, stationary means at least artially ofinsulating material forming an arc passage, means for establishing anarc within the arc passage, the first-mentioned means also providing aplurality of fluid passages spaced axially along the are passage wherebyfluid may flow through the fluid passages, and valve means including amovable apertured member for successively opening the fluid passages oneby one while at the same time successively closing others of said fluidpassages so that fluid may pass only through the fluid passages whichare opened by said valve means.

9. In a circuit interrupter, stationary means at least artially ofinsulating material forming an arc passage, means venting the arepassage only adjacent one end thereof, means for establishing an arewithin the arc passage, the firstmentioned means also providing aplurality of fluid passages disposed axially along the arc passagewhereby fluid may flow through the fluid passages into the arc passage,and valve means including a movable apertured member for successivelyopening the fluid passages one by one while at the same timesuccessively closing others of said fluid passages so that fluid mayenter the arc passage only through the fluid passages which are openedby said valve means.

10. In a circuit interrupter, stationary means at least partially ofinsulating material forming an arc passage, means for forcing fluid intothe arc passage adjacent one end thereof, means for establishin an arewithin the arc passage, the first-mentioned means also providing aplurality of spaced fluid passages extending axially along the arcpassage whereby fluid may exhaust out of the arc passage through thefluid passages, and valve means including a movable apertured member forsuccessively opening the fluid passages one by one while at the sametime successively closing others of said fluid passages so that fluidmay exhaust out of the arc passage only through the fluid passages whichare opened by said valve means.

11. In a circuit interrupter, means at least partially of insulatingmaterial forming an arc passage, means for establishing an are withinthe arc passage, the first-mentioned means also providing a plurality ofpairs of fluid passages spaced axially along the arc passage wherebyfluid may pass through each pair to strike at least opposite sides ofthe are within the arc passage, and means for successively opening thepairs of fluid passages one by one while at the same time successivelyclosing others of said pairs of fluid passages so that fluid may passonly through the pairs of fluid passages which are opened by saidlast-mentioned means.

12. In a circuit interrupter, relatively stationary means at leastpartially of insulating material forming an arc passage, means forestablishing an are within the arc passage, the first-mentioned meansalso providing a plurality of pairs of fluid passages spaced axiallyalong the arc pas- 70 2,293,833

sage whereby fluid may pass through each pair to strike at leastopposite sides of the are within the arc passage, and valve meansincluding a movable apertured member for successively opening the pairsof fluid passages'one by one while at the same time successively closingothers of said pairs of fluid passages so that fluid may pass onlythrough the pairs of fluid passages which are opened by said lastmentioned means.

13. In a circuit interrupter, stationary means at least partially-ofinsulating material forming an arc passage, means venting the arcpassage only adjacent one end thereof, means for establishing an arewithin the arc passage, the firstmentioned means also providing aplurality of fluid inlet passages disposed axially along the arc passagewhereby fluid may flow through the fluid passages into the are passage,and means for successively opening the fluid passages one by one whileat the same time successively closing others of said fluid inletpassages so that fluid may pass only through the fluid inlet passageswhich are opened by said last-mentioned means and exhaust out saidventing means.

14. In a circuit interrupter, means at least partially of insulatingmaterial forming an arc passage, means forcing fluid into the arcpassage adjacent one end thereof, means for establishing an are withinthe are passage, the first-mentioned means also providing a plurality offluid exhaust passages disposed axially along the arc passage wherebyfluid may exhaust away from the arc passage out through the fluidexhaust passages, and valve means for successively opening the fluidexhaust passages one by one while at the same time successively closingothers of said fluid exhaust passages so that fluid may exhaust out ofthe arc passage only through the fluid exhaust passages which are openedby said last-mentioned means.

15. In a circuit interrupter, relatively stationary means at leastpartially of insulating material forming an arc passage, means forestablishing an are within the arc passage, the first-mentioned meansalso providing a plurality of pairs of fluid exhaust passages spacedaxially along the arc passage whereby fluid may exhaust out of the arcpassage through the fluid exhaust passages, and valve means forsuccessively opening the pairs of fluid passages one by one while at thesame time successively closing others of said pairs of fluid passages sothat fluid may exhaust out of the arc passage only through the pairs offluid exhaust passages which are opened by said lastmentioned means.

WINTHROP M. LEEDS. BENJAMIN P. BAKER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1.955,215 Whitney et al Apr. 17,1934 2,067,643 Reher Jan. 12, 1937 2,111,416 Balachowsky Mar. 15, 19382,158,846 Balach'owsky May. 16, 1939 2,262,516 Prince Nov. 11, 1941Paxton Oct. 13, 1942

